1. Field of the Invention
The present invention relates generally to a cassette tape recorder such as a cassette video tape recorder and, more specifically, to a protected switch unit protected from dust liable to cause the faulty contact of the contact terminals, for a cassette tape recorder in which a tape loading operation, a tape unloading operation, an operation for engaging the pinch roller with the capstan and an operation for disengaging the pinch roller from the capstan are carried out by the action of a single power means through the control of an electric circuit by the action of the machine elements of a power transmission system of the cassette tape recorder.
2. Description of the Prior Art
In a conventional cassette video tape recorder (abbreviated to "VTR" hereinafter), loading and unloading a cassette are carried out by the action of a loading motor, while engaging and disengaging the pinch roller and the capstan are carried out mechanically through a lever system or the like interlocked with a control button. Such a control button, however, cannot be lightly operated.
In order to improve the accessibility of the conventional VTR, a driving mechanism which engages or disengages the pinch roller and the capstan also through electrical means, such as a small motor or a solenoid, has been proposed. However, such a driving mechanism needs a control unit for sequentially and individually actuating the loading motor, and the small motor or the solenoid at an appropriate timing. The provision of the control unit, and the small motor or the solenoid increases the size and cost of the VTR.
There has been proposed, in order to solve such a problem of the conventional driving mechanism, a driving mechanism provided with neither a small motor or a solenoid and capable of carrying out a loading operation, an unloading operation, engaging the pinch roller and the capstan and disengaging the pinch roller and the capstan with a single loading motor. Furthermore, there has been proposed an arrangement to control the operation of the loading motor of such a driving mechanism through the sliding contact between an electric circuit for driving the loading motor and a machine element of a power transmission system for transmitting the power of the loading motor.
In such an arrangement, in which the operation of the loading motor is controlled through the sliding contact between an electric circuit for transmitting the power of the loading motor and the machine element of the power transmission system, however, it is possible that dust enters the contacts of the switch unit and causes malfunction of the loading motor due to the faulty contact of the contact terminals.
The present invention has been made in view of such problems of the conventional VTR.
Accordingly, it is an object of the present invention to provide a protected switch unit protected from dust which is liable to cause faulty contact between the sliding contact terminals of the switch unit, and capable of surely controlling a single motor for a loading operation, an unloading operation, engaging the pinch roller and the capstan and disengaging the pinch roller and the capstan so that practical reliability of the VTR is improved.
The object of the present invention is achieved by a protected switch unit comprising: a circuit board of a loading motor driving circuit, disposed opposite to one surface of one machine element of a power transmission system for transmitting the power of the loading motor; a movable contact terminal fixed to the surface of the machine element facing the circuit board, so as to be in contact with the circuit formed on the circuit board for switching operatin; and a protective member disposed between the machine element of the power transmission system and the circuit board.
Preferably, the protective member is formed of an insulating material, such as a nonwoven fabric, paper felt, a synthetic resin or pottery.
Placing a protective member between the circuit board and a machine element of the power transmission system, carrying the movable contact terminal, namely, a sliding contact terminal inhibits the dust entering the switch unit, and hence prevents faulty contact between the contact terminals of the switch unit.
The above and other objects, features and advantages of the present invention will become more apparent from the following description of a preferred embodiment thereof taken in conjunction with the accompanying drawings.